According to the encyclopaedia of spices:
The nutmeg tree is a large evergreen native to the Moluccas (the Spice Islands in the East Indies) and is now cultivated in the West Indies.
It produces two spices — mace and nutmeg. Nutmeg is the seed kernel inside the fruit and mace is the lacy covering (aril) on the kernel.
The Arabs were the exclusive importers of the spice to Europe up until 1512, when Vasco de Gama reached the Moluccas and claimed the islands for Portugal.
To preserve their new monopoly, the Portuguese (and from 1602, the Dutch) restricted the trees to the islands of Banda and Amboina.